Slotted seal plates and slotted preforms for chemical vapor deposition densification

ABSTRACT

A method of making a fibrous part is provided. The method may comprise forming a porous structure with an annular geometry. A first entrance channel and a second entrance channel may be formed with the entrance channels defined by a surface of the preform. The entrance channels may also extend in a radial direction from an inner diameter of the annular porous structure partially across the surface. An exit channel may be formed between the entrance channels and defined by the surface. The exit channel may extend in a radial direction from an outer diameter of the annular porous structure partially across the surface.

FIELD OF INVENTION

The present disclosure relates to composite brakes, and, morespecifically, to slotted seal plates and slotted preforms for chemicalvapor deposition densification.

BACKGROUND

Chemical vapor infiltration and deposition (CVI/CVD) is a known processfor making composite structures such as carbon/carbon brake disks. TheCVI/CVD process typically used for making carbon/carbon brake disks mayinvolve passing a reactant gas or gas mixture (e.g., methane, propane,etc.) around heated porous structures (e.g., carbonized preforms) with apressure differential driving the gas mixture into the porousstructures. The gas enters into the porous structures, driven bypressure gradients, and undergoes a reaction such as thermaldecomposition, hydrogen reduction, co-reduction, oxidation,carbidization, or nitridation to deposit a binding matrix.

Depending on CVI/CVD methodology and conditions, the porous structuremay not densify at a uniform rate across the thickness of a porousstructure, may not form a desired microstructure, and may be associatedwith long processing times. Thus, creation of uniformly densified porousstructures may be impaired using conventional systems and methods.

SUMMARY

According to various embodiments, a method of making a fibrous part maycomprise forming a porous structure with an annular geometry. Anentrance channel may be formed with the entrance channels defined by asurface of the preform. The entrance channel may also extend in a radialdirection from an inner diameter of the annular porous structurepartially across the surface. An exit channel may be defined by thesurface. The exit channel may extend in a radial direction from an outerdiameter of the annular porous structure partially across the surface.

In various embodiments, the method may comprise densifying the porousstructure using a pressure gradient chemical vapor deposition process.The method may also comprise the steps of pressing a channel into asecond surface of the porous structure, stacking a second porousstructure over the first porous structure, and/or disposing a seal platebetween the first porous structure and the second porous structure. Asecond exit channel may be formed in a surface of the second porousstructure. The surface of the first porous structure may be stackedagainst the surface of the second porous structure with the second exitchannel and the entrance channel staggered. A gas may be urged into theentrance channel, through the porous structure, and out the exitchannel. The method may also include the steps of using a high-flowchemical deposition process to densify the porous structure and using athermal gradient chemical deposition process to densify the porousstructure.

According to various embodiments, a method of making a fibrous part maycomprise placing a composite part having an annular geometry into achemical vapor infiltration (CVI) vessel, and placing a seal plate overa surface of the composite part. The seal plate may comprise an entrancechannel in a surface of the seal plate and extending in a radialdirection from an inner diameter of the seal plate partially across thesurface. The seal plate may also comprise an exit channel defined by thesurface and extending in a radial direction from an outer diameter ofthe seal plate partially across the surface.

In various embodiments, the method may include densifying the porousstructure using a pressure gradient chemical vapor deposition process. Agas may be urged into the first entrance channel, through the porousstructure, and out the exit channel. A high-flow chemical depositionprocess may be used to densify the porous structure. A thermal gradientchemical deposition process may also be used to densify the porousstructure. A second porous structure may be placed in the vessel withthe seal plate between the first porous structure and the second porousstructure.

According to various embodiments, a fibrous part may comprise a porousstructure having an annular geometry. A surface of the porous structuremay define a first entrance channel that extends in a radial directionfrom an inner diameter of the porous structure partially across thesurface. The surface may also define an exit channel that extends in theradial direction from an outer diameter of the porous structurepartially across the surface.

In various embodiments, the porous structure may comprise layers. Thelayers may be bonded together using a chemical vapor infiltration (CVI)process. A second entrance channel may be defined by the surface of theporous structure. The second entrance channel may extend in the radialdirection from the inner diameter of the porous structure partiallyacross the surface. The exit channel may be disposed between the firstentrance channel and the second entrance channel.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the figures, wherein like numerals denotelike elements.

FIG. 1 illustrates a CVI vessel densifying a stack of porous materials,in accordance with various embodiments;

FIG. 2 illustrates an annular seal comprising channels formed partiallythrough the seal in both radial and axial directions, in accordance withvarious embodiments;

FIG. 3 illustrates gas dispersing from channels in a seal through anannular preform; in accordance with various embodiments;

FIG. 4 illustrates an annular preform having channels formed partiallythrough the preform in both radial and axial directions, in accordancewith various embodiments;

FIG. 5A illustrates a channel arrangement with entry channels and exitchannels staggered and disposed on opposite surfaces of an annularpreform, in accordance with various embodiments;

FIG. 5B illustrates a channel arrangement with entry channels alignedwith entry channels in an axial direction and exit channels aligned withexit channels in the axial direction, in accordance with variousembodiments;

FIG. 5C illustrates a channel arrangement with entry channels alignedwith exit channels in an axial direction, in accordance with variousembodiments;

FIG. 5D illustrates stacked preforms having entry channels aligned withadjacent entry channels and exit channels aligned with adjacent exitchannels, in accordance with various embodiments; and

FIG. 6 illustrates the flow of gas through an annular preform startingfrom an entrance channel and exiting through an exit channel, inaccordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice theexemplary embodiments of the disclosure, it should be understood thatother embodiments may be realized and that logical changes andadaptations in design and construction may be made in accordance withthis disclosure and the teachings herein. Thus, the detailed descriptionherein is presented for purposes of illustration only and notlimitation. The steps recited in any of the method or processdescriptions may be executed in any order and are not necessarilylimited to the order presented.

Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact. Surface shading lines may be used throughout thefigures to denote different parts but not necessarily to denote the sameor different materials.

Referring to FIG. 1, an exemplary fixture 10 in a chemical vaporinfiltration (CVI) vessel is shown for pressure gradient CVI in a stackof porous structures 12, in accordance with various embodiments. Porousstructures 12 may have “OD” (outside diameter) seal plates 14 disposedaround the outside diameter of porous structures 12. Porous structures12 may also have “ID” (inside diameter) seal plates 16 disposed aroundthe inside diameter of porous structures 12. The OD seal plates 14 mayhave an inside diameter 18 slightly less than the porous structureoutside diameter 22, and an outside diameter 20 that may be generallycoterminous with the porous structure outside diameter 44. The ID sealplates 16 may have an outside diameter 24 slightly greater than theporous structure inside diameter 26, and an inside diameter 28 that maybe generally coterminous with the porous structure inside diameter 26.With ID seal plates 16, the porous structure outside diameter 22 may begreater than said outside diameter 24 of the ring like ID seal plate 16.Seal plate 14 and seal plate 16 may be disposed between porousstructures 12 to provide spacing.

In various embodiments, seal plates 14 and seal plates 16 may providesealing between external volume 40 and internal volume 42. A pressuregradient may be maintained between external volume 40 and internalvolume 42 to encourage gas 46 to travel from internal volume 42 throughporous structures 12. Gas 48 moves through porous structures 12 frominternal volume 42 to external volume 40 and exits from vessel 52. Asgas 48 moves through porous structures 12, gas deposits may densifyporous structures 12.

With reference to FIG. 2, a seal plate 100 is shown, in accordance withvarious embodiments. Seal plate 100 may have an annular geometry withouter surface 102 (also referred to herein as outer diameter). Sealplate 100 may also have an inner surface 104 (also referred to herein asan inner diameter). Entrance channels 108 and exit channels 106 may beformed partially through an axial thickness of seal plate 100. Althoughentrance channels 108 and exit channels 106 are labeled “entry” and“exit” the gas flow direction may be reversed by reversing the directionof the pressure gradient, in which case gas would exit from entrancechannels 108 and enter into exit channels 106.

In various embodiments, entrance channels 108 may be equally spacedabout inner diameter 104 of seal plate 100 in a circumferentialdirection. Exit channels 106 may also be equally spaced about outerdiameter 102 in a circumferential direction. Exit channels 106 mayextend only partially across seal plate 100 in a radial direction toprevent forming an open gas path from inner diameter 104 to outerdiameter 102. Similarly, entrance channels 108 may be formed onlypartially across seal plate 100 in the radial direction. As used herein,“only partially” across or through a surface may describe a channelformed in a surface of a seal or preform that either opens to an outerdiameter and terminates in the surface or opens to an inner diameter andterminates in the surface. As used herein, a radial direction may be ina direction of a radius of a circular part, such as a seal or preform,or more generally a direction moving from an inner diameter towards anouter diameter or from an outer diameter towards an inner diameter.

In various embodiments, entrance channels 108 and exit channels 106extending only partially through seal plate 100 in a radial directionenable a pressure gradient densification. Entrance channels 108 and exitchannels 106 may not be formed completely across seal plate 100 in aradial direction as channels completely across seal plate 100 may tendto equalize a pressure gradient from inner diameter 104 to outerdiameter 102. Seal plate 100 may comprise exit channels 106 and entrancechannels 108 formed in a top surface 110, a bottom surface opposite thetop surface, or both.

With reference to FIG. 3, two seal plates 100 are shown with preform 120between seal plates 100 for CVI densification, in accordance withvarious embodiments. Preform 120 may be a fibrous part such as a brakepart for an aircraft. Seal plates may comprise exit channels 106starting at outer diameter 102 and entrance channels 108 starting atinner diameter 104 to provide spacing from preform 120. Preform 120 maybe a porous structure.

The porous structure (i.e., preform 120) may comprise at least one ofcarbon, silicon carbide, silicon nitride, boron carbide, aluminumnitride, titanium nitride, boron nitride, zirconia, SiCxNy (wherein x isa number in the range from about zero to about 1, and y is a number inthe range from about zero to about 4/3), silica, alumina, titania(TiO2), and a combination of at least two of the foregoing. Prior todensification, the porous structure may be referred to as a preform. Apreform for use in making a carbon/carbon composite, such as acarbon/carbon disk brake, may be referred to as a carbonized preform.

As used herein, the term “porous structure” may be interchangeable with“porous structure system.” A porous structure system may comprise one ormore porous structures that are associated. For example, a porousstructure system may comprise two porous structures coupled so thatthere is contact between each porous structure, such as in a “stack.” Aporous structure system may comprise three or four porous structurespositioned so that at least two of the component porous structures arein contact with each other. For example, a porous structure system maycomprise four porous structures positioned in a stack formation. Porousstructures may be formed using one or more unbounded and/or separatelayers and consolidating the layers into one continuous part during CVI.In that regard, seal plates 100 with channels may be pressed ontoseparate layers and the layers may be bonded together by the CVIprocess.

A porous structure may comprise any porous structure derived from afibrous material such as carbon fibers, silicon carbide fibers, and thelike. The carbon fibers may be derived from polyacrylonitrile, rayon(synthetic fiber derived from cellulose), pitch, and the like. Thefibrous material may be in the form of a woven, braided or knittedfabric or a needled felt. The fibrous material may be in the form ofchopped carbon fibers molded to form a preform. Prior to thedensification process, the fibrous material may be formed into a preformhaving any desired shape or form.

The porous structure may be in the form of a disk having any shape suchas, for example, a polygon, a cylinder, a triangle, square, rectangle,pentagon, hexagon, octagon, and the like. In addition, the porousstructure may have an irregular form.

A pressure differential between inner diameter 104 and outer diameter102 may urge gas through the fibrous material and subsequently depositcarbon material in the fibrous material. Gas may pass from innerdiameter 104 into entrance channel 108. Gas in entrance channel 108 maymove through the fibrous material of preform 120. Gas 124 may travelthrough an axial thickness of preform 120 towards an exit channel 106and towards outer diameter 102. Gas 122 may move between entrancechannel 108 and adjacent exit channel 106 in a circumferentialdirection.

The exit channels 106 and entrance channels 108 formed in seal plate 100may expose an increased surface area of preform 120. Gas may enterpreform 120 through surfaces of entrance channel 108 as well as throughinner diameter of preform 120. Gas may also exit preform 120 throughexit channels 106 as well as outer diameter of preform 120. Theincreased external surface area of preform 120 exposed to gas mayprovide advantageous densification speed and uniformity.

With reference to FIG. 4, a preform 200 is shown (similar to preform 120of FIG. 3), in accordance with various embodiments. Preform 200 may haveentrance channels 208 and exit channels 206 formed in surface 210. Withbrief reference to FIG. 2, entrance channels 208 and exit channels 206may be similar in geometry and orientation to entrance channels 108 andexit channels 106 of seal plate 100. The fibrous material of preform 200may be a porous structure, as described above with reference to FIG. 3.Entrance channels 208 and exit channels 206 may be formed by applyingpressure to preform 200 by depressing a mold or fixture having negativechannels to act as a stamp. Entrance channels 208 may extend radiallyoutward from inner diameter 204 and partially across surface 210 in aradial direction. Similarly, exit channels 206 may extend radiallyinward from outer diameter 202 and extend partially across surface 210.Entrance channels 208 and exit channels 206 extending only partiallythrough preform 200 in a radial direction enable a pressure gradientdensification. Entrance channels 208 and exit channels 206 may not beformed completely across preform 200 in a radial direction as channelscompletely across preform 200 may tend to equalize a pressure gradientfrom inner diameter 204 to outer diameter 202.

With reference to FIGS. 5A-5D, exemplary orientations of entrancechannels 208 and exit channels 206 are shown, in accordance with variousembodiments. In FIG. 5A, exit channels 206 are formed in surface 230 ofpreform 200A and entrance channels 208 are formed in surface 232 ofpreform 200A. Entrance channels 208 are offset from exit channels 206 inan x direction (on the xy axis provided for ease of illustration). Thedepth (in the y direction) of entrance channels 208 and exit channels206 as well as the distance (in the x direction) between entrancechannels 208 and exit channels 206 may be selected to optimize gas flowfrom entrance channel 208 to exit channel 206.

With reference to FIG. 5B, exit channels 206 and entrance channels 208are formed in both surface 230 and surface 232 of preform 200B. Entrancechannels 208 in surface 232 are formed axially adjacent (i.e., in the ydirection) to an entrance channel 208 formed in surface 230. Similarly,exit channels 206 in surface 232 are formed axially adjacent to an exitchannel 206 formed in surface 230. In that regard, an exit channel 206may be disposed between two entrance channels 208. Similarly, anentrance channel 208 may be disposed between two exit channels 206. Thedepth (in the y direction) of entrance channels 208 and exit channels206 as well as the distance (in the x direction) between entrancechannels 208 and exit channels 206 may be selected to optimize gas flowfrom entrance channel 208 to exit channel 206.

With reference to FIG. 5C, exit channels 206 and entrance channels 208are formed in both surface 230 and surface 232 of preform 200C. Entrancechannels 208 in surface 232 are formed axially adjacent (i.e., in the ydirection) to an exit channel 206 formed in surface 232. Similarly, exitchannels 206 in surface 232 are formed axially adjacent to an entrancechannel 208 formed in surface 230. The depth (in the y direction) ofentrance channels 208 and exit channels 206 as well as the distance (inthe x direction) between entrance channels 208 and exit channels 206 maybe selected to optimize gas flow from entrance channel 208 to exitchannel 206.

With reference to FIG. 5D, stacked preforms 200D are shown, inaccordance with various embodiments. Stacked preforms 200D have exitchannels 206 aligned with adjacent exit channels 206 (i.e., adjacent inthe y direction). Stacked preforms 200D also have entrance channels 208aligned with adjacent entrance channels 208 (i.e., adjacent in the ydirection). Aligned exit channels 206 and aligned entrance channels 208enable a pressure gradient from inner diameter of preform 200D to outerdiameter of preforms 200D. Exit channel 206 may also be staggeredrelative to entrance channel 208. Exit channel 206 may not be alignedwith entrance channel 208 in the y direction to avoid forming a directgas path that does not go through fibrous material from inner diameterto outer diameter of preform 200D.

With reference to FIG. 6, gas is shown flowing through the fibrousmaterial of preform 200, in accordance with various embodiments. Aninner volume 220 may supply pressurized gas for CVI in preform 200.Inner volume may be raised to a higher pressure than outer volume 222 tocreate a pressure gradient between inner volume 220 and outer volume222. The pressure gradient may drive gas 224 into entrance channel 208.Gas may fill entrance channel 208 and diffuse laterally and radiallyinto fibrous material of preform 200 in a direction generally movingfrom inner diameter 204 to outer diameter 202. A portion of gas 226 maydiffuse laterally from entrance channel 208, through fibrous material ofpreform 200, and into exit channel 206. Gas 228 may then exit preform200 via exit channel 206.

In various embodiments, multiple preforms 200 may be stacked in a vesselfor CVI without spacers between the preforms. Preforms in a stackwithout spacers may be aligned having entrance channels 208 in a surfaceof a first preform staggered from exit channels 206 in a surface of asecond preform that contacts the surface the first preform. Staggeringthe channels tends to prevent a direct gas path (i.e., without passingthrough fibrous material of preform 200) from inner volume 220 to outervolume 222. Preforms in a stack may have entrance channels 208 of thepreforms aligned and exit channels 206 of the preforms aligned withoutforming a direct gas path from inner volume 220 to outer volume 222.Stacked preforms 200 directly contacting one another may conserve volumein a CVI vessel to enable a greater number of preforms 200 to fit intothe vessel compared to stacked preforms 200 with spacers betweenpreforms 200.

In various embodiments, the pressure gradient CVI of the presentdisclosure may be carried out at an elevated temperature. The elevatedtemperatures may be uneven and controlled so that a temperature gradientis created. A temperature gradient may vary the rate of depositionduring the CVI process to further improve uniformity of the deposition.The pressure gradient CVI may be carried out with a ratio of per-minutegas flow to preform volume greater than or equal to 1.5 (also referredto as high-flow CVI). For example, if 15,000 cubic centimeters (915cubic inches) of gas were flowing per minute over a 10,000 cubiccentimeter (610 cubic inches) then part the ratio of per-minute gas flowto preform volume would be 1.5. The higher ratios of per-minute gas flowto preform volume may accelerate the densification process due to theincreased area in which gas can escape through the part. The increasedsurface area provided by entrance channels 208 and exit channels 206 mayenable high-flow CVI with improved uniformity of deposition and increasethe rate of densification. Additionally, increased volume and area thatis exposed to the pressure gradient may further enhance densification athigh flow rates.

Benefits and other advantages have been described herein with regard tospecific embodiments. Furthermore, the connecting lines shown in thevarious figures contained herein are intended to represent exemplaryfunctional relationships and/or physical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships or physical connections may be present in apractical system. However, the benefits, advantages, and any elementsthat may cause any benefit or advantage to occur or become morepronounced are not to be construed as critical, required, or essentialfeatures or elements of the disclosure. The scope of the disclosure isaccordingly to be limited by nothing other than the appended claims, inwhich reference to an element in the singular is not intended to mean“one and only one” unless explicitly so stated, but rather “one ormore.” Moreover, where a phrase similar to “at least one of A, B, or C”is used in the claims, it is intended that the phrase be interpreted tomean that A alone may be present in an embodiment, B alone may bepresent in an embodiment, C alone may be present in an embodiment, orthat any combination of the elements A, B and C may be present in asingle embodiment; for example, A and B, A and C, B and C, or A and Band C.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “various embodiments”, “oneembodiment”, “an embodiment”, “an example embodiment”, etc., indicatethat the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same embodiment.Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described. After reading the description, itwill be apparent to one skilled in the relevant art(s) how to implementthe disclosure in alternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f), unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A method of making a fibrous part, comprising:forming a porous structure with an annular geometry; forming an entrancechannel defined by a surface of the porous structure and extending in aradial direction from an inner diameter of the porous structure onlypartially across the surface; forming an exit channel defined by thesurface and extending in the radial direction from an outer diameter ofthe porous structure only partially across the surface; and densifyingthe porous structure using a pressure gradient chemical vaporinfiltration process.
 2. The method of claim 1, wherein the forming theentrance channel comprises pressing the entrance channel into thesurface of the porous structure.
 3. The method of claim 1, furthercomprising stacking a second porous structure over the porous structure.4. The method of claim 3, further comprising disposing a seal platebetween the porous structure and the second porous structure.
 5. Themethod of claim 3, further comprising: forming a second exit channel ina surface of the second porous structure; and stacking the surface ofthe porous structure against the surface of the second porous structurewith the second exit channel and the entrance channel staggered.
 6. Themethod of claim 1, further comprising urging a gas into the entrancechannel, through the porous structure, and out the exit channel.
 7. Amethod of making a fibrous part, claim 1, further comprising: forming aporous structure with an annular geometry; forming an entrance channeldefined by a surface of the porous structure and extending in a radialdirection from an inner diameter of the porous structure only partiallyacross the surface; forming an exit channel defined by the surface andextending in the radial direction from an outer diameter of the porousstructure only partially across the surface; and densifying the porousstructure using a thermal gradient chemical deposition process.
 8. Themethod of claim 7, wherein the forming the entrance channel comprisespressing the entrance channel into the surface of the porous structure.9. The method of claim 7, further comprising stacking a second porousstructure over the porous structure.
 10. The method of claim 9, furthercomprising disposing a seal plate between the porous structure and thesecond porous structure.
 11. The method of claim 9, further comprising:forming a second exit channel in a surface of the second porousstructure; and stacking the surface of the porous structure against thesurface of the second porous structure with the second exit channel andthe entrance channel staggered.
 12. A method of making a fibrous part,comprising: forming a porous structure with an annular geometry; formingan entrance channel defined by a surface of the porous structure andextending in a radial direction from an inner diameter of the porousstructure only partially across the surface; forming an exit channeldefined by the surface and extending in the radial direction from anouter diameter of the porous structure only partially across thesurface; and stacking a second porous structure over the porousstructure.
 13. The method of claim 12, further comprising disposing aseal plate between the porous structure and the second porous structure.14. The method of claim 12, further comprising: forming a second exitchannel in a surface of the second porous structure; and stacking thesurface of the porous structure against the surface of the second porousstructure with the second exit channel and the entrance channelstaggered.
 15. The method of claim 12, further comprising urging a gasinto the entrance channel, through the porous structure, and out theexit channel.
 16. The method of claim 12, further comprising using achemical infiltration process to densify the porous structure.
 17. Themethod of claim 12, further comprising densifying the porous structureand the second porous structure using a thermal gradient chemicaldeposition process.
 18. The method of claim 12, further comprisingdensifying the porous structure and the second porous structure using apressure gradient chemical vapor infiltration process.